Because it’s Friday: Visualizing an email chain

We’ve all been there: someone sends an email to a mailing list with a Reply-To directing responses back to the mailing list. Before long, someone replies (unwittingly, to everyone) to ask to be taken of the list. And before long, the entire affair devolves into an endless cycle of requests to unsubscribe and pleas to stop mailing the entire list. This process is visualized beautifully in this timeline of emails to the Caltrans Performance Measurement System mailing list (click to see the enlarged original on FlowingData):

Some of the classic r-help threads could also benefit from such a treatment.